1. Field of Invention:
This invention relates generally to dental X-ray aiming devices adapted to place an X-ray film packet having sharp edges in the oral cavity of a patient at a proper position therein before the packet is exposed to X-rays, and in particular to a device of the type which includes a holder for the film packet that serves to shield the sharp edges thereof so as to avoid direct contact with tissue within the oral cavity and the resultant discomfort, pain or trauma.
2. Status of Prior Art:
Dental X-ray technology affords useful information regarding the structural integrity of the teeth and its supporting tissue. Commonly used for the purpose of producing a radiograph of a tooth region is a film packet in which a chip of X-ray film is disposed within a rectangular plastic carrier that is permeable to X-rays but not to light rays, so that the film housed therein is exposed only when subjected to X-rays.
In practice, the film packet is placed in a patient's oral cavity behind a tooth region to be X-rayed and is then exposed to radiation passing through the region onto the emplaced film packet. In order to minimize distortion of the radiograph, a "paralleling" technique is used in which the film packet is maintained in parallel relation to the long axis of the teeth.
To this end, use is made of a dental X-ray aiming device that includes a film holder having integral therewith a bite block that projects from the rear of the holder and is clenched between the teeth of the patient. The film packet, which is held in the holder behind the tooth region to be X-rayed, is then substantially parallel with the long axis of the teeth.
Detachably coupled to the bite block of the film holder is a guide rod on which is slidable a sighting ring through which is projected an X-ray beam that is directed toward the film packet held behind the tooth region of interest. One such dental X-ray aiming device is disclosed in the U.S. Pat. No. 4,965,885, to Fuhrmann. In this device, the film packet is inserted in a holder formed by a plate whose upper edge is U-shaped and a lower clamp that acts to ensure a better hold and exact positioning of the film packet. A similar dental X-ray aiming device is disclosed in the Updegrave U.S. Pat. No. 3,473,026.
In a typical film packet, the flat, rectangular plastic film carrier which envelops the X-ray film chip is heat-sealed around its perimeter to provide thin, flexible edges so that the packet is bendable. These edges are relatively sharp; hence when the film packet is placed within the oral cavity of a patient, its edges then engage soft tissue and may cause discomfort, intensive pain, or even trauma when pressed into the tissue by a dental operator seeking to properly place the film packet so as to obtain a good radiograph.
Even greater difficulty is experienced with children or adults having small mouths, as well as with those adults who exhibit sensitive bony projections inside the mandible and the hard palate. Yet if the film packet is shifted within the oral cavity to a more comfortable position, then the film packet may not be properly placed. Or if the patient will only bite gently on the bite block until the film packet meets resistance by soft tissue, then the film packet will not be firmly held in place, and the quality of the resultant radiograph may be adversely affected.
In order to overcome this problem, the U.S. Pat. Nos. 4,626,216 and 4,805,201, to Strong-Grainger, provide a soft, foam plastic padding for a dental X-ray film packet. The soft padding is either incorporated into the structure of the film packet or takes the form of a separate pad for attachment to a standard film packet.
The U.S. Pat. No. 5,044,008, to Jackson, discloses a frame-like, foam plastic cushion for a dental film packet. In the U.S. Pat. No. 4,847,884, to Dove, a holder is provided in the form of a soft cylinder having a slot therein to receive one edge of the film packet.
Also of background interest are the following patents:
Van Aken--U.S. Pat. No. 4,707,847 PA1 McAuslan--U.S. Pat. No. 4,592,084 PA1 Updegrave--U.S. Pat. No. 3,003,062